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ARTICLE

The ocean in action – introduction

The ocean is part of our lives – we may swim in it, sail on it or eat food from it. Many aspects of the ocean affect us – it controls climate, supports life, wears away land, and provides ...

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ARTICLE

Marine food webs

Feeding relationships are often shown as simple food chains – in reality, these relationships are much more complex, and the term ‘food web’ more accurately shows the links between producers ...

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ARTICLE

Ocean salinity

There are many chemicals in seawater that make it salty. Most of them get there from rivers carrying chemicals dissolved out of rock and soil. The main one is sodium chloride, often just called ...

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ARTICLE

The ocean and the carbon cycle

The ocean plays an important role in the global carbon cycle. Carbon moves in and out of the ocean daily, but it is also stored there for thousands of years. The carbon cycle Carbon is a chemical ...

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ARTICLE

Waves as energy transfer

‘Wave’ is a common term for a number of different ways in which energy is transferred: In electromagnetic waves, energy is transferred through vibrations of electric and magnetic fields. In sound ...

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ARTICLE

Cleaning up the oil spill

On 5 October 2011, the cargo vessel Rena ran aground on the Astrolabe Reef. The ship was carrying 1700 tonnes of heavy fuel oil and about 200 tonnes of diesel in its tanks. Over 360 tonnes of ...

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ARTICLE

Ocean dissolved gases

Seawater has many different gases dissolved in it, especially nitrogen, oxygen and carbon dioxide. It exchanges these gases with the atmosphere to keep a balance between the ocean and the ...

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ARTICLE

Ocean temperature

The temperature of the ocean determines what form the water takes. Most of the ocean is liquid water, but if it gets cold enough, it turns to solid ice, or if it gets hot enough, it can pass into ...

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ARTICLE

Ocean density

The density of seawater plays a vital role in causing ocean currents and circulating heat because of the fact that dense water sinks below less dense. Salinity, temperature and depth all affect ...

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ARTICLE

Behaviour of waves

All waves behave in certain characteristic ways. They can undergo refraction, reflection, interference and diffraction. These basic properties define the behaviour of a wave – anything that ...

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ARTICLE

Water density

Water density changes with temperature and salinity. Density is measured as mass (g) per unit of volume (cm³). Water is densest at 3.98°C and is least dense at 0°C (freezing point). Why does ice ...

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ARTICLE

Adapting to marine habitats

Being able to adapt is a matter of life or death. In a perfect world, organisms would not need to adapt. However, changes to the environment and food web mean that organisms need to move, if they ...

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ARTICLE

Water and weather

The water cycle is driven by energy from the sun. Liquid water is evaporated and changed into a gas. In this process, energy is absorbed (endothermic). The gaseous vapour rises and circulates in ...

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ARTICLE

Fundamentals of waves

Seeing, hearing, feeling warmth, surfing, tuning the radio, using a cellphone – these and many more activities involve waves. But what is a wave? In this article, we get to grips with the ...

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ARTICLE

Continental drift

The Earth’s continents have not always been where they are at present. If you look at a map of the world, you might notice what Alfred Wegener noticed – that the continents look as if they could ...

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ACTIVITY

Build a marine food web

In this activity, students build their own food web using images of organisms from the marine ecosystem. This activity can be done indoors on paper or outdoors on a tarmac surface using chalk. By ...

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The ocean and Earth’s systems and cycles

The ocean plays an important part in several Earth systems and cycles. This is hardly surprising, as it covers two-thirds of the planet’s surface. It is difficult to study any of these systems ...

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ARTICLE

Ocean motion

The ocean has a complex circulation system, moving water, heat, salt and nutrients around the world. Surface currents in the top 400m are driven mainly by wind. Deeper currents are driven by ...

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